1. Field of the Invention
The present invention relates to a release binding for telemark skiing, back country skiing and ski jumping. This invention also relates to an insert in the sole of the boot, which is indispensable for the functioning of the binding-boot assembly.
It relates more specifically to a binding that is adapted to ensure retention of the front portion of the boot on the ski.
2. Description of Background and Relevant Information
The bindings commonly used in the aforementioned sports are constituted by a metallic stirrup fixed on the ski and adapted to receive the front end of the boot. The boot is maintained in the stirrup by:
a journalled breeching, described in the French Patent No. 2.147.218; or
a cable gripping the sole, described in the European patent No. 0.495.192.A1.
In bindings of the aforementioned type, an escape of the boot from the ski is possible only voluntarily, by opening of a latch (removal of the boot). In the case of a fall, the tip of the boot remains affixed to the ski, which can constitutes a danger for the skier in certain fall configurations, especially those with a substantial torsional component. The relative movement between the leg and the ski, which is present in this type of fall, can no longer be compensated for by increasingly rigid boots for practicing on acclivous grounds.
Certain telemark competitors use release binding initially designed for cross country skiing. This type of binding includes a rigid plate on which a previously described stirrup binding is fixed, and an assembly integrated or attached to the ski to enable the escape of the plate under a substantial torsional force. This assembly which allows safety is constituted by a single piston including a spring whose tip is housed in the front end of the plate, and by an abutment element located behind the latter, which maintains it in place under the pre-stress generated by said piston.
In the release bindings of the aforementioned type, the release releases are ill-timed due to a basic boot retention and safety system which operates with a single pre-stress. This action of the piston, in the ski axis, also causes a stiffening of the ski in the location of said plate, beneath the boot. Most spare-time and cross-country skiers consider the change in the rigidity of the skis, which are very flexible, as well as the substantial weight of the assembly of the constituent elements as serious drawbacks: safety on the ski, binding without safety and plate.
Furthermore, during an intensive practice, a majority of skiers note a pain on their toes, caused by a point transmission of the forces between the boot and the ski, in the area of the front end of the boot.